The signaling function of sharing fake stories

The fluorescent Ca2+ indicator fura 2 was used to measure cytosolic free [Ca2+] ([Ca2+]i) in order to obtain information about relative rates of Ca2+ influx into parietal cells during treatment with carbachol (a cholinergic agonist) or thapsigargin (TG, a Ca(2+)-mobilizing agent) or during reloading of the internal Ca2+ stores. In Ca(2+)-containing solutions, carbachol-, TG-, and reloading-stimulated Ca2+ entry exhibited nearly identical sensitivity to La3+ [inhibition constant (Ki) approximately 10 microM] or low pH (pKi approximately 7.0). In experiments in which carbachol and TG were used, there was no additional increase in [Ca2+]i when TG was added to carbachol-treated cells or when carbachol was added to cells previously treated with TG. Thus it is likely that a single Ca2+ entry pathway serves a signaling function as well as a role in refilling the Ca2+ store during reloading. Because the Ca2+ pathway is exquisitely sensitive to pH and serosal pH increases during stimulant-induced H+ secretion (which is activated by increases in [Ca2+]i), this mechanism will exert positive feedback on parietal cells in the intact stomach. When parietal cells were pretreated with carbachol in Ca(2+)-free solutions, reloading was independent of pH and La3+, suggesting that Ca(2+)-containing solutions should be used to determine the properties of the influx pathway.

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Towards Understanding Extracellular ROS Sensory and Signaling Systems in Plants

Advances in Botany ◽

10.1155/2014/538946 ◽

2014 ◽

Vol 2014 ◽

pp. 1-10 ◽

Cited By ~ 16

Author(s):

Saijaliisa Kangasjärvi ◽

Jaakko Kangasjärvi

Keyword(s):

Reverse Genetics ◽

Stomatal Closure ◽

Air Pollutant ◽

Cellular Functions ◽

Alarm Signal ◽

Signaling Systems ◽

Signaling Function ◽

Electron Transport Chains ◽

Response To Stress ◽

Ros Formation

Reactive Oxygen Species (ROS) are ubiquitous metabolites in all aerobic organisms. Traditionally ROS have been considered as harmful, accidental byproducts of cellular functions involving electron transport chains or electron transfer. However, it is now recognized that controlled production of ROS has significant signaling functions, for example, in pathogen defense, in the regulation of stomatal closure, or in cell-to-cell signaling. ROS formation in subcellular compartments is critical to act as “alarm” signal in the response to stress, and the concept of ROS as primarily signaling substances has emerged. The involvement of ROS in several developmental and inducible processes implies that there must be coordinated function of signaling network(s) that govern ROS responses and subsequent processes. The air pollutant ozone can be used as a useful tool to elucidate the function of apoplastic ROS: O3 degrades in cell wall into various ROS which are interpreted as ROS with signaling function inducing downstream responses. We have used ozone as a tool in mutant screens and transcript profiling-reverse genetics to identify genes involved in processes related to the signaling function of ROS. We review here our recent findings in the elucidation of apoplastic ROS sensing, signaling, and interaction with various symplastic components.

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The Na/K-ATPase Signaling: From Specific Ligands to General Reactive Oxygen Species

International Journal of Molecular Sciences ◽

10.3390/ijms19092600 ◽

2018 ◽

Vol 19 (9) ◽

pp. 2600 ◽

Cited By ~ 11

Author(s):

Rebecca Pratt ◽

Cameron Brickman ◽

Cameron Cottrill ◽

Joseph Shapiro ◽

Jiang Liu

Keyword(s):

Reactive Oxygen Species ◽

Positive Feedback ◽

Reactive Oxygen ◽

Underlying Mechanism ◽

Short Review ◽

Oxygen Species ◽

Signaling Function ◽

Amplification Loop

The signaling function of the Na/K-ATPase has been established for 20 years and is widely accepted in the field, with many excellent reports and reviews not cited here. Even though there is debate about the underlying mechanism, the signaling function is unquestioned. This short review looks back at the evolution of Na/K-ATPase signaling, from stimulation by cardiotonic steroids (also known as digitalis-like substances) as specific ligands to stimulation by reactive oxygen species (ROS) in general. The interplay of cardiotonic steroids and ROS in Na/K-ATPase signaling forms a positive-feedback oxidant amplification loop that has been implicated in some pathophysiological conditions.

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Mechanisms of calcium signaling by cyclic ADP-ribose and NAADP

Physiological Reviews ◽

10.1152/physrev.1997.77.4.1133 ◽

1997 ◽

Vol 77 (4) ◽

pp. 1133-1164 ◽

Cited By ~ 256

Author(s):

H. C. Lee

Keyword(s):

Nitric Oxide ◽

Nicotinic Acid ◽

Live Cells ◽

Release Mechanism ◽

Major Mechanism ◽

Signaling Mechanisms ◽

Signaling Function ◽

Cyclic Adp Ribose ◽

Inositol 1,4,5 Trisphosphate ◽

External Signals

Cells possess various mechanisms for transducing external signals to intracellular responses. The discovery of inositol 1,4,5-trisphosphate (IP3) as a messenger for mobilizing internal Ca2+ stores has centralized Ca2+ mobilization among signaling mechanisms. Results reviewed in this article establish that, in addition to IP3, the internal Ca2+ stores can be mobilized by at least two other molecules, cyclic ADP-ribose (cADPR) and nicotinic acid adenine dinucleotide phosphate (NAADP), via totally independent mechanisms. Cyclic ADP-ribose is a newly discovered cyclic nucleotide derived from NAD, but, unlike adenosine 3',5'-cyclic monophosphate, its main signaling function is modulation of Ca(2+)-induced Ca2+ release, a major mechanism of Ca2+ mobilization in addition to the IP3 pathway. Evidence shows that cADPR may in fact be responsible for mediating the Ca(2+)-mobilizing activity of the gaseous messenger nitric oxide. Cells responsive to cADPR are widespread and include species from plant to mammal, indicating the generality of cADPR as a signaling molecule. In addition to cADPR, NAADP, a metabolite of NADP, can also mobilize Ca2+ stores. The release mechanism and the stores on which NAADP acts are distinct from cADPR and IP3. Nicotinic acid adenine dinucleotide phosphate may play a role in generating Ca2+ oscillations, since liberation of NAADP in live cells by photolyzing its caged analog produces long lasting Ca2+ oscillations. These two new Ca2+ agonists are intimately related, since the same metabolic enzymes can, under appropriate conditions, synthesize either one, suggesting a unified mechanism may regulate both pathways. Elucidation of these two new Ca2+ mobilization pathways is likely to have an important impact on our understanding of cellular signaling mechanisms.

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The CD3 chains of the T cell antigen receptor associate with the ZAP-70 tyrosine kinase and are tyrosine phosphorylated after receptor stimulation.

Journal of Experimental Medicine ◽

10.1084/jem.178.5.1523 ◽

1993 ◽

Vol 178 (5) ◽

pp. 1523-1530 ◽

Cited By ~ 84

Author(s):

D B Straus ◽

A Weiss

Keyword(s):

T Cell ◽

Tyrosine Kinase ◽

Tyrosine Phosphorylation ◽

Kinase Activity ◽

Antigen Receptor ◽

Tyrosine Kinase Activity ◽

Cell Antigen Receptor ◽

Cell Antigen ◽

Signaling Function ◽

Signaling Events

Recent work indicates that signaling events resulting from stimulation of the T cell antigen receptor (TCR) can be initiated by the CD3 complex (gamma, delta, epsilon) as well as the zeta chains of the receptor. To help characterize the signaling function of CD3 we examined its associated tyrosine kinase activity since induction of tyrosine phosphorylation is one of the earliest signaling events. Our results indicate that at least two kinases, lck and ZAP-70, contribute to the CD3-associated kinase activity. A likely target of this activity is the CD3 complex itself since we observed that TCR stimulation resulted in rapid tyrosine phosphorylation of the CD3 epsilon and delta chains. To examine the function of the CD3 epsilon chain in particular, we constructed a chimera that fused the extracellular and transmembrane domains of CD8 to the cytoplasmic domain of CD3 epsilon. This chimera demonstrated that CD3 epsilon was independently capable of associating with proteins having tyrosine kinase activity, including ZAP-70. Our results show that the kinase activity that associates with the CD3 complex has characteristics that are quite similar to the previously characterized zeta-associated kinase activity. This finding suggests that both these components of the TCR initiate signaling events using a common mechanism. However, differences in their signaling function could result from recognition of distinct substrates.

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Emotion Generation Based on a Mismatch Theory of Emotions for Situated Agents

Handbook of Research on Synthetic Emotions and Sociable Robotics ◽

10.4018/978-1-60566-354-8.ch014 ◽

2009 ◽

pp. 247-266 ◽

Cited By ~ 2

Author(s):

Clément Raïevsky ◽

François Michaud

Keyword(s):

Decision Making ◽

Life Forms ◽

Current Situation ◽

Human Beings ◽

Signaling Function ◽

Emotion Generation ◽

Collective Foraging ◽

Mismatch Theory ◽

Artificial Model ◽

Made In

Emotion plays several important roles in the cognition of human beings and other life forms, and is therefore a legitimate inspiration for providing situated agents with adaptability and autonomy. However, there is no unified theory of emotion and many discoveries are yet to be made in its applicability to situated agents. One function of emotion commonly identified by psychologists is to signal to other cognitive processes that the current situation requires an adaptation. The main purposes of this chapter are to highlight the usefulness of this signaling function of emotion for situated agents and to present an artificial model of anger and fear based on mismatch theories of emotion, which aims at replicating this function. Collective foraging simulations are used to demonstrate the feasibility of the model and to characterize its influence on a decision-making architecture.

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